Electrodynamic machine



July 21, 1959 J. S.-AXELSON ELECTRODYNAMIC MACHINE Filed Dec. 9, 1957[ht/677:0)", Jahri Axe/$027, y %W./% m

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United States Patent C) ELECTRODYNAMIC MACHINE John S. Axelson, Erie,Pa., assignor to General Electric Company, a corporation of New YorkApplication December 9, 1957, Serial No. 701,532

4 Claims. (Cl. 310-51) are laid in slots provided in the armaturecore'and are held in place by wedges of wood or other suitable material.On larger machines, the windings and wedges are further held in place byoverlying binding or retaining bands, the latter being provided at oneor more places over the periphery of the central portion of thearmature, as well as at the ends of the armature where the individualwindings are connected together and to the commutator. The binding bandsare required to prevent the wedges and individual windings from flyingout of their slots under the influence of centrifugal force when thearmature is rotating, as well as to keep the end portions of thewindings and their connections in place under such conditions. For sometime, metal bands or wires were employed to bind the windings in placein the armature core, and any dynamic balancing of the armature requiredwas performed by rotating the armature in any of the well-known dynamicbalancing devices, and applying metal solder or molten metal to themetal bind ing bands, preferably the end bands which are usually atreduced portions of the armature and are not critical in so far asclearance with the stator or other parts of the machine is concerned.The metal so applied was then adjusted and trimmed as required toachieve perfect dynamic balancing of the armature. While such metalbinding bands serve their purpose, they are undesirable from some pointsof view. Extreme care must be taken during installation of such bandsboth to insure that they are tight enough and also to insure that theydo not cut into the winding insulation, particularly at the end portionswhere they are laid directly over the windings. Any such metal bindingbands that Work loose because of improper fitting or which because ofsharp edges or for other reasons cut into the insulation, induce failureof the machine. The use of solder or other relatively low melting pointmetal on such metal bands as a balancing medium involves the removal ofinsulating varnish from the band, cleaning, and the application of flux.Furthermore, should the rotor overheat, such heat is quite readily anddirectly transmitted to the solder through the metal bands, causingearly melting and subsequent failure of the machine.

An improvement in armature or rotating part binding bands was broughtabout when resin-impregnated tape or roving was introduced for thispurpose, the tape being wound tightly around the armature under tension,and cured to form a unitary band, which was both easier to apply thanmetal and much less likely to cut into the insulation. Furthermore, asthe tape was cured in place,

location on the band determined.

Patented July 21, 1959 varnish. Tape of glass fiber cloth of variousweaves or of essentially parallel filament glass roving or tape aregenerally preferred for such binding bands, although when the stressconditions are not as stringent, other fabrics or fibers such as ofpaper, cellulose, asbestos, or parallel filament constructions, etc. canbe used. However, despite the many advantages of resin-impregnatedbinding bands, there has been no convenient way of attaching to them aweighting material which would permit the ready balancing of armaturesor rotating parts to which they are mounted since the conventional useof solder is not applicable to resin-impregnated bands. As a result,even where resin-impregnated binding bands are used, the end bands arenormally still of metal and the balancing of the armature isaccomplished by means of solder or similar metal applied to such metalbands.

A principal object of this invention is to provide ready means forbalancing armatures or other rotating parts of electrodynamic machinerywherein resin-impregnated binding bands are employed.

Briefly, the invention comprises means for balancing rotatable membersof electrodynamic machinery having resin-impregnated binding bandswherein a material comprising a metal-filled resin or one which isfilled with other high density material and which is compatible withthat of the resin in the binding band is employed. In balancing anarmature or similar part in accordance with this invention, the part issimply placed in any well known balancing device, rotated, and theamount of balancing material necessary for balancing and its proper.Then the spot on the binding band where the balancing material is to beapplied is cleaned, as with a solvent, and the proper amount ofmetal-filled resinous material applied thereto and cured in place.

- balancing material is readily accomplished by abrading it bondedtightly to the underlying resin of the insulating or scraping excessmaterial from the main body of balancing material or, conversely, byadding more of the metal-filled material to the same or other spots onthe binding band.

Those features of the invention which are believed to be novel are setforth with particularity in the claims appended hereto. The invention,along with its method of operation, will, however, be better understoodfrom a consideration of the following description and the drawing, inwhich the single figure is a perspective view of an armature memberillustrating the invention.

Any of the usual thermosetting resins can be used in conjunction withthe invention so long as the resin used will adhere to the binding bandand its impregnant. Dependent upon this condition, phenolic type resinscan be used as can polyesters and silicone resins, as well as urea andmelamine-formaldehyde type resins, among others. Those resins known asepoxide, ethoxyline or epoxy resins are particularly well adapted to thepresent use since they are compatible with most other resins and willadhere tenaciously thereto. Generally, such epoxy resins comprise apolyether derivative of a polyhydric organic compound, said derivativecontaining 1,2 epoxy groups, the compound being selected from the classconsisting of polyhydric alcohols and phenols containing at least twophenolic hydroxy groups. For example, US. Patent 2,324,483 to Castandiscloses epoxy resin compositions comprising the reaction product ofphenols having at least two phenolic hydroxy groups and anepihalogenohydrin such as epichlorohydrin, the product having at leasttwo epoxy groups and being cured to a thermoset, infusible mass by theuse of a carboxylic or polybasis acid or acid anhydride such as phthalicanhydrides. Other acid type curing agents for epoxy resins includehexachloroendomethylenetetrahydrophthalic anhydride, maleic anhydrideand pyromellitic dianhydride. The use of Any further adjustment 'of theorganic nitrogen base or amine type materials to cure epoxy resins isalso well known as set forth, for example, in Patent 2,444,333, suchmaterials often giving a rapid cure at room temperature. The use ofboron trifiugrideamine complex materials as epoxy resin curing agents isalso well known as disclosed, for example, in Greenlee Patent 2,717,885.United States Patents 2,494,295; 2,500,600 and 2,511,913 describefurther ethoxyline resins which can be used in conjunction with thisinvention and the above patents are all hereby incorporated by referencein this application.

The ethoxyline resins preferably used herein have more than one epoxygroup per molecule. They can be prepared by reacting a polyhydroxyalcohol or phenol, such as hydroquinone, resorcinol, glycerin andcondensation products of phenols with ketones, for example, bis-(4-hydroxy phenyl)-2,2-propane with epichlorohydrin. The reaction ofepichlorohydrin with bis-(4-hydroxy phenyl) 2,2propane is as follows:

able. When cured, the putty is readily trimmed by filing or by othermethods.

Example 2 To 80 parts of Epon 828 and parts of Epi-Rez 507 there wereadded 850 parts of powdered lead and about 5 parts of glass fibershaving an average length of about inch, and parts pyromelliticdianhydride. The conconsistency of this material again was about that ofa iers p t Shown in the drawing is armature 1 which is typical of therotatable parts which can be dynamically balanced according to thisinvention. Mounted upon shaft 2 are laminations which make up armaturecore 3 having longitudinal slots 4 in which are mounted coils 5 held inplace in the slot portions by wedges 6. Commutator 7 mounted toward oneend of the shaft 2 serves as a curent coll tor. A u e p r phery of h m tco e prep r i m un ed at least e, and pr fe a ly, as

where n has an average value ranging from 0 to about 10. Such ethoxylineresins are sold under the name of Epon by Shell Chemical Corporation,under the name Araldite by the Ciba Company, as Epi-Rez resins byDevoe-Raynolds Company, and ERL resins by the Bakelite Company. The datagiven below for such resins is representative.

Any high density filler can be used in conjunction with the resinousmaterial. Generally, a material such as lead is preferred because itwill afford the greatest weight per unit volume and permit the use ofsmaller amounts of balancing material. However, it is to be understoodthat this does not preclude the use of other metals in connection withthe present invention provided they do not melt at the operatingtemperature under the operating temperature of the device. Other highdensity materials can be used, such as red iron oxide, etc.

The following examples are illustrative of a composition which is usefulin connection with the invention and are not to be taken as limiting.All parts are by weight.

Example 1 With 25 parts of Epon 828 there were mixed about 227 parts byweight of powdered lead resulting in a mixture having the consistency ofglaziers putty. There were mixed with this material two parts ofdiethylenetriamine as a curing agent. The cure time for this resin isfrom about 1 to 3 minutes under an infrared heat lamp of the usual type.For example, a five hundred watt lamp held at a distance of 2 to 3inches from the band is suitsuitable tool.

shown, a plurality of binding or retaining bands 8 which serve to retainwedges 6 and windings 5 in place in the core slots when the armature isrotating at high speeds. Additional binding bands are provided at theends of the armature core where the windings 5 are drawn togetherfor'interconnecting as at 9 and at 10 where they are attached to thecommutator. As pointed out above, it has been found that resinimpregnated fibrous material makes an economical band which is as strongas metal bands and does not have the disadvantages of; the latter.

In carrying out the invention, the armature, including the binding bandsafter assembly, is placed in a dynamic balancing machine of any wellknown type and rotated. When the point at amount of unbalance isdetermined, the surface of one or both ofthe end binding bands asindicated is cleaned and the filled resin with curing agent as describedabove applied thereto and more or less flattened out as shown in 11 or12 with a spatula or other The resin is cured in any convenient mannor,for example, by placing an infrared lamp near the resin. The resin ofExample 1 will cure to a hard thermoset state in about two minutes undersuch treatment and the resin of Example 2 takes about three minutes tocure under like conditions. Other means of curing may be used, such asoven treatment, etc.

'When the filled resin balancing weight has been cured, the armature isonce again placed in the dynamic bal ancing apparatus and tested. If theweight added is too great, it may be readily trimmed down to properweight as byfiling. More weight, if indicated, is added as above.

{Ilhere are provided by this invention means and methods for balancingthe armatures or other rotating parts of electrodynamic or othermachinery which utilize resin impregnated binding or retaining bands forretaining the rotating assembly in place against the action ofcentrifugal force. It will be realized, of course, that the presentbalancing means can also be used for metal bands as well as when thebase is a material such as an epoxy resin, etc, which readily adheres tometal. The use of high temperature resistant resin, such as that ofExample 2, using -a pyromellitic dianhydride cured epoxy resin,perrrritsthe operation of machinery at temperatures up to the order ofabout C. without disrupting the balance ofthe armature. In the practiceof the present invention,

the resin acts as an insulation and retainer for the high density metalor other filler so that it does not melt even under the most stringentoperating conditions in which the temperature might actually exceed themelting point of the filler.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A rotating member for an electrodynamic machine having at least oneresin-impregnated band therearound, at least one of said bands havingadherent thereto a resin material filled with a relatively high densityfiller.

2. A rotating member for an electrodynamic machine having at least oneresin-impregnated binding band therearound, at least one such bindingband having adherent thereto an epoxy resin filled with a relativelyhigh density material for balancing purposes.

3. The process of dynamically balancing a rotating part for anelectrodynamic machine, said part having at least one resin reinforcedbinding band, which process comprises applying to at least one suchbinding band a resin filled with a relatively high density material insuch quantity and at such point which balances said rotating part.

4. The process of dynamically balancing a rotating member for anelectrodynamic machine, said machine having at least one resinreinforced binding band, which process comprises applying to at leastone such band an epoxy resin filled with a relatively high densitymaterial to balance said member.

References Cited in the file of this patent Glass Tape for ArmatureBanding, from Railway Locomotives and Cars, December 1957, pp. 38 and39.

